Sunday, April 24, 2011

Contagious Habits: How Obesity Spreads | Wired Science | Wired.com

A few years ago, Nicholas Christakis and James Fowler made a striking discovery about obesity: it spreads from person to person, much like a contagious virus. They were able to demonstrate this by mining the data sets of the Framingham Heart Study (FHS), a longitudinal survey that has revealed many of the risk factors underlying cardiovascular disease. Because the FHS noted each participant’s close friends, colleagues, and family members, Christakis and Fowler were able to recreate the social network of the town, to see how everyone was connected to everyone else.

And this is when they made their remarkable discovery about weight gain. According to the data, if one person became obese, the likelihood that his friend would follow suit increased by 57 percent. (This means that the network is far more predictive of obesity than the presence of genes associated with the condition.) If a sibling became obese, the chance that another sibling would become obese increased by 40%, while an obese spouse increased the likelihood that the other spouse would become obese increased by 37%.

The Christakis/Fowler work is an important reminder that Donne was right: No man is an island/entire of itself. Instead, we are all plugged into a vast network of social contacts and cultural norms. While we think ourselves as autonomous individuals, that autonomy is severely constrained by those around us.

But this longitudinal data – it’s a bird’s eye view of human life – still begs the question: How do other people influence us? Why does an obese friend make us so much more likely to gain weight? Why do the habits of others influence our own habits?